Often times we get asked, "What's the difference between a Super 110 and, say, a Super 150?"
First, we have to start with what the Super number signifies. Originally, there were several different ways to measure the fineness of wool. This study from New Mexico State University does a pretty good job at outlining the beginnings of wool grading. Before the advent of certain technologies, there was a weight system using big spools of wool called hanks that held 560 yards of yarn. If a wool fiber was finer, more hanks were produced, eventually yielding a more luxurious cloth.
Nowadays we use the diameter of the wool fiber, a measurement taken in microns (a millionth of a meter), to determine the fineness. For most of the fine wool in the world, that measurement falls between 12-20 microns, with the vast majority sitting between 15-18. That measurement is then converted back into the the original Super grading system.
So, a Super 120's yarn equates to 17.5 microns and a Super 150's yarn equates to 16 microns. It is important to point out that these numbers have no relation to thread count, which pertains to cotton fabrics. It is also important to point out which mill mills the wool into a textile. Technically speaking, you can microwave wagyu beef. Or, it can be prepared by a chef. Which sounds better?
The unspoken mission of most clients who enjoy the plight of custom clothing is to find a fabric that is fine enough while still remaining durable and cost effective. Sometimes it's finding a mill that makes fabric you like more than another, regardless of fineness.
A Super 200, 13.5 micron wool fiber produces an incredibly luxurious and expensive fabric. It is also a fabric that cannot be beaten up. Typically, the higher the Super number, the less durable the fabric. A Super 130, 17 micron wool fiber is a wonderfully durable and fine yarn. However, some clients prefer a Super 120 or a Super 150.
Which is better? It depends. Next time you're in the shop, ask to feel fabrics from each range and see for yourself.